Heretofore, as a method for preparing a nitrile compound, a carboxylic acid compound or a carboxylic acid ester compound from an acetic acid compound, it has been known, for example, a method in which acetonitrile is obtained by heating cyanoacetic acid to 160° C. or higher (for example, see Chem. Ber., 7, 1382 (1874)) or a method in which acetic acid is obtained by heating malonic acid in p-azoxyanisole at 141° C. (for example, see J. Indian Chem. Soc.,58, 868 (1981)). However, in either of the above-mentioned methods, high reaction temperatures are required, and yields are low or there is no description about yields, etc., so that these methods are not satisfied as an industrial process for preparing a nitrile compound, a carboxylic acid compound or a carboxylic acid ester compound.
Also, as a method for preparing 4-substituted tetrahydropyran from 4-substituted tetrahydropyran-4-carboxylic acid, or from bis(2-halogenoethyl)ether and 2-substituted acetic acid ester, it has been known a method, for example, in which bis(2-chloroethyl)ether and ethyl cyanoacetate are reacted to prepare ethyl 4-cyanotetrahydropyran-4-carboxylate, then the resulting material is hydrolyzed to prepare 4-cyanotetrahydropyran-4-carboxylic acid, and further, it is heated at 180 to 200° C. to produce 4-cyanotetrahydropyran with overall yield of 12.2% (for example, see J. Chem. Soc., 1930, 2525). Also, it has been known a method in which bis(2-chloroethyl)ether and diethyl malonate are reacted to prepare diethyl tetrahydropyran-4,4-dicarboxylate, then, the resulting material is hydrolyzed to prepare tetrahydropyran-4,4-dicarboxylic acid, and then, the resulting material is heated to 180° C. to prepare tetrahydropyran-4-carboxylic acid with overall yield of 31.8% (for example, see Helv. Chim. Acta., 80, 1528 (1997)). However, in either of the above-mentioned methods, high reaction temperatures are required, and yields are low, so that these methods are not satisfied as an industrial process for preparing 4-substituted tetrahydropyran.
Moreover, as a method for preparing 4-aminomethyl-tetrahydropyran and an acid salt thereof from 4-cyanotetrahydropyran, it has been known a method, for example, in which 4-cyanotetrahydropyran and hydrogen are reacted in the presence of Raney nickel in anhydrous ethanol (for example, see International Patent Publication No. 94/05639). However, according to this method, yield of the objective product, 4-aminomethyltetrahydropyran, is low, and a large amount of a by-product (bis(4-tetrahydropyranylmethyl)amine) is produced, etc., so that this is not satisfied as an industrial process for preparing 4-aminomethyltetrahydropyran and an acid salt thereof.